Plug-in bus duct

ABSTRACT

A plug-in bus duct comprised of a group of elongated, flat busbars positioned in side-by-side relation within an elongated housing, the housing having the side walls of a height substantially greater than the width of the busbars. Insulator sheets separate the busbars one from the other, and from the sides of the housing, to form a side wall-insulator sheet-busbar &#39;&#39;sandwich.&#39;&#39; In preferred form, the busbars are all of the same cross-sectional configuration and dimensions, and each retains a planar configuration along its entire length from one end of the duct to the other. This construction leaves the top and bottom edges of the busbars exposed within the housing. An insulator template is installed in each of a plurality of openings cut in the top and bottom of the housing at spaced intervals therealong. Each template cooperates with the insulator sheets to define a series of stab chambers insulated one from the other, each stab chamber being partially defined by an exposed busbar edge; each chamber is adapted to receive one stab from a plug unit in a manner that permits the stab to make contact with the exposed edge of the busbar in that chamber, thereby allowing power to be taken off the bus duct through the plug unit and dispersed into power leads. A cover is provided for each of the housing&#39;&#39;s openings, the cover being pivotable between a position at which the stab chambers are opened to receive the plug unit&#39;&#39;s stabs and a position at which the stab chambers are closed.

Unite States Patent [191 Hater 1 May 1,1973

[54] PLUG-IN BUS DUCT [75] Inventor: Paul M. Hater, Florence, Ky.

[73] Assignee: Arrow-Hart, Inc., Hartford, Conn.

[22] Filed: Aug. 30, 1971 [21] Appl. No.: 176,001

52 US. Cl ..339/22 B, 174/68 B 51 Int. Cl. ..H01r 13/60 [58] Field ofSearch ..339/22 B, 22 R, 262;

174/99 B, 88 B, 68 B, 71 B [56] References Cited UNITED STATES PATENTS2,968,781 1/1961 Staskowski ..339/22 3,482,202 12/1969 Wallace et al....339/22 B 3,009,011 11/1961 Fisher ..l74/88 3,614,297 10/1971Carlson.... ...l74/88 B 3,636,237 1/1972 Hafer ..l74/68 B PrimaryExaminer-Marvin A. Champion Assistant Examiner-Robert A. HaferAtt0meyEdward B. Evans et al.

[57] ABSTRACT A plug-in bus duct comprised of a group of elongated, flatbusbars positioned in side-by-side relation within an elongated housing,the housing having the side walls of a height substantially greater thanthe width of the busbars. Insulator sheets separate the busbars one fromthe other, and from the sides of the housing, to form a sidewall-insulator sheet-busbar sandwich. In preferred form, the busbars areall of the same crosssectional configuration and dimensions, and eachretains a planar configuration along its entire length from one end ofthe duct to the other. This construction leaves the top and bottom edgesof the busbars exposed within the housing. An insulator template isinstalled in each of a plurality of openings cut in the top and bottomof the housing at spaced intervals therealong. Each template cooperateswith the insulator sheets to define a series of stab chambers insulatedone from the other, each stab chamber being partially defined by anexposed busbar edge; each chamber is adapted to receive one stab from aplug unit in a manner that permits the stab to make contact with theexposed edge of the busbar in that chamber, thereby allowing power to betaken off the bus duct through the plug unit and dispersed into powerleads. A cover is provided for each of the housings openings, the coverbeing pivotable between a position at which the stab chambers are openedto receive the plug units stabs and a position at which the stabchambers are closed.

15 Claims, 9 Drawing Figures Patented May 1, 1973 3,731,256

4 Sheets-Sheet 2 Patented May 1, 1973 3,731,256

4 Sheets-Sheet 4 I NVEN TOR.

PLUG-IN BUS over This invention relates to bus ducts and, moreparticularly, relates to a novel plug-in bus duct.

Electric power distribution systems in industrial and commercialbuildings utilize busbars to transfer electric power from a substationor transformer bank to a power consuming area. Such power distributionsystems are generally made up of a plurality of bus ducts of variablelengths, the bus ducts being connected or interlocked one to the otherin end-to-end relation by a suitable busbar coupler system to provideelectrical continuity between the power source and the power consumingarea.

A bus duct is comprised of a group of elongated busbars supported ininsulated relation relative one to the other within an elongatedhousing. One type of bus duct structure that has recently been marketedis that type having a plurality of elongated, flat busbars positioned inside-by-side relation within a housing, the housing having a pair ofelongated side walls ofa height substantially greater than the width ofthe busbars. The busbars and housing side walls are separated one fromthe other only by insulation means of the type generally having athickness less than the thickness of a single busbar. Bus ducts of thisgeneral design have been found particularly desirable for use inrelatively low voltage value situations, for example, 600 volts andbelow, as well as in relatively high amperage value situations, forexample, 100 amperes and over. Such a bus duct structure has been foundparticularly useful in certain applications because both reactance andimpedance are decreased for a given length of bus duct. That is, for agiven length of this type bus duct the voltage drop has been found to beless than in a bus duct construction where the busbars may be separatedin their side-by-side relation by, for example, air spaces. Further,this type bus duct structure has been found more efficient indissipating heat created within the busbars when same are loaded withthe maximum or approximately maximum amperage capacity. Additionally,the size and weight of a bus duct having this type structure isminimized, thereby making final installation of the duct easier for thecontractor.

In the power consuming area which an electric power distribution systemserves, the lengths of the bus duct are provided with a specialstructural configuration at one or more points along their length thatpermits power to be taken off and distributed to machinery or the likein that area. The specially configured bus duct that permits power to betaken offintermediate its length is generally known as a plug-in busduct. With all plug-in bus ducts, a plug unit is required to tap powerfrom the bus duct and transfer it into power leads. There are manydifferent types of plug unit designs and, as a matter of fact, generallyspeaking each manufacturer designs his own plug unit for use with hisown plug-in bus duct. Because of this approach to the creation of apower distribution system, the bus duct line marketed by a manufacturermust include a plug-in bus duct and a plug unit, thereby allowing powerto be tapped from any given bus duct run at a desired point therealongand transferred through power leads to the power consuming area.

One bus duct structure of the type described (i.e., of the type wherethe busbars are separated one from the other and from the sides of thehousing only by insulation positioned therebetween, where the insulationis of a lesser thickness than the thickness of the busbars, and wherethe housings side walls are substantially greater in height than thewidth of the busbars) is particularly set forth in US. Pat. applicationSer. No. 70,010, invented by Paul M. Hafer, filed Sept. 8, 1970, andassigned to the assignee of this application. The bus duct structuretaught in that application provides a couple .of distinct advantagesover similar type bus duct structures known to the art. For example, thebus duct structure taught in that application is comprised of simpleparts and is easy to assemble during manufacture, thereby providingeconomical manufacturing costs. Further, the bus duct structure taughtin that application does not require insulative wrapping of the busbars,does not require special assembling of the busbars into a preformedassembly, does not require special bonding agents for adhering thehousing side walls to the busbar assembly, and does not require weldingequipment for achieving the final housing configuration.

This invention is directed to a novel plug-in bus duet structure of thattype wherein the busbars are separated one from the other, and from thesides of the housing, only by insulator sheets positioned therebetweento form a side wall-insulator sheet-busbar sandwich. In preferred form,the busbars are all of the same cross-sectional configuration anddimensions, and each retains a planar configuration along its entirelength from one end of the duct to the other. Such a structuralconfiguration leaves the top and bottom edges of the busbars exposedwithin the housing. According to the principles of this invention, aninsulator template is installed in each of a plurality of openings cutin the top and bottom of the housing at spaced intervals therealong.Each template cooperates with the insulator sheets to define a series ofstab chambers insulated one from the other, each stab chamber beingpartially defined by an exposed busbar edge; each chamber is adapted toreceive one stab from a plug unit in a manner that permits the stab tomake contact with the exposed edge of the busbar in that chamber,thereby allowing power to be taken off the bus duct through the plug anddispersed into power leads. A cover is provided for each of the housingsopenings, the cover being pivotable between a position at which the stabchambers are opened to receive the plug units stabs and a position atwhich the stab chambers are closed.

Therefore, it has been one objective of this invention to provide aplug-in bus duct that is basically comprised of a group of elongated,flat busbars positioned in sideby-side relation within an elongatedhousing, the busbars being separated one from the other only byinsulation that is of a lesser thickness than the thickness of thebusbars and the housing having side walls of a height substantiallygreater than the width of the busbars.

It has been another objective of the invention to provide a plug-in busduct of the type set out in the above paragraph in which the busbarsretain their planar configuration from one end of the bus duct to theother, i.e., do not have ofiset or other type deformations in theplug-in area of the bus duct that are especially adapted for a plugunit.

It has been another objective of the invention to provide a plug-in busduct of the type set out in the above two paragraphs that makes use ofinsulator sheets positioned between the busbars, and between the busbarsand side walls, to form a side wall-insulator sheetbusbar sandwich, sucha structure leaving the top and bottom edges of the busbars exposed.

It has been a further objective of this invention to provide a plug-inbus duct that utilizes the structural concepts of that bus ductstructure taught in U.S. Pat. application Ser. -No. 70,010 filed Sept.8, 1970, invented by Paul M. Hafer, and assigned to the assignee of thisapplication.

Other objectives and advantages of this invention will be more apparentfrom the following detailed description taken in conjunction with thedrawings in which:

FIG. 1 is a perspective view of the plug-in bus duct of this inventionand a plug unit adapted for use therewith;

FIG. 2 is a side cross-sectional view of one of the ducts take-offsections and is taken along line 2-2 of FIG. 1;

FIG. 2A is an enlarged fragmentary view of one encircled area of FIG. 2;

FIG. 2B is an enlarged fragmentary view of another encircled area ofFIG. 2;

FIG. 3 is an end cross-sectional view taken along line 3--3 of FIG. 2,and also showing a plug unit in operating engagement with the take-offsection;

FIG. 4 is a partially exploded, partially broken away perspective viewof a take-off section;

FIG. 5 is a perspective view of the unitary reinforcing member used oneach side of a take-off section;

FIG. 6 is a perspective view of the underside of an insulator templateused at eachtake-off section; and

FIG. 7 is a perspective view of a covers latch from the undersidethereof.

As illustrated in FIGS. 1, 2, 3, and 4, the plugin bus duct 10 of thisinvention includes a housing 11 and a group of separate, elongated, flatbusbars 12a, 12b, 12c positioned in sideby-side relation within thehousing. The busbars 12 are of substantially the same externaldimensions, and are positioned in a group having opposite edges l3, 14in a substantially common plane to forma rectangular cross-section,i.e., the cross-sectional configuration and dimensions of one busbar isthe same as that of all others, see FIGS. 3 and 4. A series of separate,flat, elongated insulator sheets 15 are positioned between adjacentbusbars 12, and between each of the housings side walls 16 and theoutermost busbars 12a, 12c of the group, to insulate the busbars onefrom the other and from the housings side walls. Note that, in thissandwich' relationship of the busbars l2a-l2 and insulator sheets 15,the busbars are each of a planar configuration along the entire lengthof each busbar from one end of the bus duct 10 to the other. Thus, theinsulator sheets 15 and the busbars 12 are arranged flatwise inside-by-side relation and lie parallel with the housings side walls 16.This is true even in the plug-in areas or take-off sections 51 locatedalong the bus ducts length, i.e., no offset or other specialconfiguration for the busbars is provided in the take-off sections 51,thereby providing a less complex plug-in bus duct structure in thetake-off sections of the bus duct than is usually found in bus ducts ofthe plugin type.

Referring to FIG. 3, note that the height H of the housings side walls16 is substantially greater than the width W of the busbars 12, thewidth of each busbar being equal to the width of all other busbars.Also, note that each of the insulator sheets is of a width Wsubstantially greater than the width W of the busbars l2, and eachinsulator sheets width dimension W is preferably on the order of theinside height dimension H of the housings sides 16. Also note that thethickness of the insulator sheets 15 is substantially less than thethickness of the busbars 12.

The side walls 16 of the bus ducts housing 11 are comprised of channelsections which face toward one another and are telescoped into oneanother when finally assembled, see FIGS. 3 and 4. The housings top 17and bottom 18 are also channel sections, and these sections also facetoward one another but are sufficiently spaced away one from the otherso that they do not in any sense telescope one within the other whenfinally assembled. The busbars 12 are centered relative to the housingsside walls 16, that is, the busbars are spaced equally from the housingstop 17 and bottom 18, so that an air gap 19 is provided above the topedge 13 of the busbars and an air gap 22 is provided below the bottomedge 14 of the busbars, see FIGS. 3 and 4. As shown in the Figures, theinsulator sheets 15 extend a substantial distance into the air gaps 19,22 and extend up adjacent to the top edges 27 of side walls 16 andadjacent the bottom edges 29 of the side walls.

Such a width dimension W of the insulator sheets 15 acts to preventelectrical creepage between adjacent busbars l2 and between theoutermost busbars and the housings sides 16. I I

At least-two U-shaped clips-26 are positionedto span the housings sidewalls 16 at separate positions longitudinally spaced from onev anotheralong the top edges 27 of the side walls, the spanningportion'28 of eachof the clips beingsubstantially spaced above top edge 13 of the busbarsand in substantially the same plane as the housings top 17, see FIGS. 3and 4. Likewise at least two U-shaped clips 26 are positioned to spanthe housings side walls 16 at separate positionslongitudinally spacedfrom one another along the bottom edges 29 of the side walls, thespanning portion 28 of each of these clips being substantially spacedbelow bottom edge 14 of the busbars and in substantially the same planeas the housings bottom 18. The clips 26 are provided to restrainmechanically the busbar 12 group, the insulator sheets 15, and the sidewalls 16 in compact, assembled side-by-side relation. Thatis, clips 26hold the busbars l2, insulator sheets 15, and side walls 16 infunctional assembly by squeezing the side walls toward one another,thereby acting to maintain the busbar-insulator sheet-side wallcombination or sandwich in the desired spatial and operationalconfiguration. When in locking or clamping position after assembly ofthe bus duct, the legs 33 of each clip 26 are positioned on the outsideof the side walls l6 and the clips spanning portion 28 spans the sidewalls. The clips 26 are preferably positioned in pairs longitudinarilyalong the bus duct, each pair comprising a top clip and a bottom clipand each pair being disposed in a plane substantially transverse to theaxis of the bus duct, see FIGS. 2, 3 and 4.

The bus ducts housing 11 is additionally provided with a plurality ofreinforcement members 35 in the form of heavy-duty channels, theheavy-duty channels 35 being positioned against each of the side walls16, see FIGS. 14. Each reinforcement member 35 forms a part of acomplete force frame surrounding the busbars 12, insulator sheets 15 andside walls 16, the force frame for holding the busbars 12 and insulatorsheets 15 is assembled sandwich relation thus including clips 26, sidewalls 16 and reinforcement members of the heavy-duty channels 35. Eachof the heavy-duty chan' nels 35 is positioned substantially transverseto the axis of the bus duct against the housings side walls 16, and aheavy-duty channel 35 is positioned to cooperate with each pair of theU-shaped clips 26 on each side of the bus ducts housing. The width ofthe spanning portion 28 of each U-shaped clip 26 is sufficient to permitthe legs 33 to embrace the two heavy-duty channels 35 positioned onopposite sides of the housing 11 against the housings side walls 16, aswell as the group of busbars 12, insulator sheets and the side walls.

A bracket 37 is welded to the upper end and to the lower end of eachheavy-duty channel 35, see FIGS. 2, 3, 4, and 5. Each bracket 37includes a base portion 38 having an elongated slot 39 therein; the baseis integral with leg portions 41 that are welded to the inside offlanges 42 of the reinforcement member 35. Each leg 41 of the bracket 37has a guide strip 43 formed thereon. The guide strips 43 are thus fixedto the heavyduty channel 35 since the bracket 37 is welded thereto. Theguide strips 43 of each bracket are positioned such that a gap isprovided between the guide strips and the base 44 of the heavy-dutychannel 35 after welding the two parts together. The legs 33 of The legsU-shaped clip 26 are received in the slots so defined when the U- shapedclip is assembled with the busbar 12-insulator sheet 15-side wall 16sandwich. This structure prevents the legs 33 of the clips 26 fromflaring outwardly in times of high short circuit stress and serves toreinforce the bus duct assembly.

The elongated slot 39 in each bracket 37 is positioned to receive bolts40 which pass through suitable holes in the top 17 and bottom 18 of thehousing 11, the top and bottom of the housing thereby being bolted tothe brackets 37. Thus, the top 17 and bottom 18 are indirectly fixed tothe side walls 16 through brackets 37 that are mounted (for example,welded) to heavy-duty channels or rigid support members 35.

Each length of the plug-in bus duct of this invention has at least onetake-off section 51 located in either the top 17 or bottom 18 of theduct. Preferably, however, the take-off sections 51 are located togetherin pairs along the axial length of the plug-in bus duct, one beingprovided in the top 17 of the duct every time one is provided in thebottom 18 of the duct; with such a structure the installer of theplug-in bus duct need not worry as'to which is the top and which is thebottom of the duct. Further, more than one pair of take-off sections 51may be provided in each length of plug-in bus duet, the number of pairsprovided being dependent on the end use of the bus duct and the numberof power takeoffs required in the power consuming area. The portion ofplug-in bus duct 10 illustrated in FIG. 1 includes two pairs of take-offsections 51, each pair having a take-off section in the housings top 17and a take-off section in the housings bottom 18.

Each take-off section 51 is located between two successive pairs ofvertical reinforcing members 35. Corresponding notches or sections 52are cut out of the top edge (and/or bottom edge) of the telescopedtogether side walls 16; note that only the side walls are so notched,thereby leaving the insulator sheets 15 extending up into the opening ornotches cut into the side walls, see particularly FIG. 4. Thisconstruction makes the top edges 13 of the busbars 12 accessible fromoutside the duct since the busbars are not covered with any insulationon the top edges 13 or bottom edges 14 thereof.

A horizontal reinforcing member 53 is welded between the two verticalreinforcing members 35 located at each end of the side wall notches 52,see FIGS. 4 and 5. Thus, in each take-off section 51 area of the busduct 10, two successive vertical reinforcing members 35 are fixedtogether one with the other by a horizontal reinforcing member 53 toform an H-shaped reinforcing part 54 as illustrated in FIG. 5, one ofthese parts 54 being located against the outside of each side wall 16.The I-I-shaped reinforcing parts 54 are held in fixed relation with theducts housing 11 and, in fact, serve to hold the busbars l2-insulatorsheets 15 and side walls 16 in operable assembly, by U-shaped clips 26.The horizontal reinforcing member 53 is also of a channel-shapedconfiguration with the base 55 thereof flush against the side wall 16 ofthe housing 1 1, thereby adding two more fins in the form of channelsides 56 by which heat can be dissipated to the atmosphere in thetake-off area. The I i-shaped parts 54 cooperate with U- shaped clips 26to further reinforce the housing 11 in that area of the take-off sectionwhen same is provided with a plug 61 for power take-off or simply duringnormal usage of the bus duct, such being desirable because of thenotches 52 cut in side walls 16.

The opening 52 cut in the side walls 16 at the top thereof receives atemplate 57, see FIGS. 4 and 6. The template 57 is formed of aninsulating material and is provided with a number of grooves 58 in itsbottom face 65 equal to the number of insulator sheets 15 that separatethe busbars 12 one from the other and that separate the housings sidewalls 16 one from the other. The grooves 58 are of a width substantiallyequal to the thickness of the insulator sheets 15, and the grooves areof a depth sufficient to embrace the insulator sheets when the template57 is located thereon as illustrated in FIG. 3. The template 57 is alsoprovided with a series of slots 59 therethrough from the top face 64 tothe bottom face 65, the slots being equal in number to the number ofbusbars 12 carried by the housing. The slots 59 are not located inalignment transverse to the bus ducts axis 45, but are instead staggeredaxially of the bus ducts axis in the template 57 so that not more thanevery other slot is located in the same transverse plane. This providesadded rigidity to the template from a mechanical strength standpointand, further, provides added rigidity to the insulator sheets 15 in thenotch 52 area of the take-off section 51.

In the case of the two stabs slots 59a, 59b, an insulative rib 66 ispositioned between the insulator sheets 15 that embrace busbar 12b so asto aid in preventing damage to those insulator sheets when the plugsstabs 60 are in place and to provide additional electrical insulationbetween the stabs, see FIGS. 3 and 6. In the case of the stab slot 59c,insulative ribs 67 are located in between the insulator sheets 15 whichembrace busbars 12a and 120 for the same purpose. Thus, the insulativetemplate 57 is received in the opening 52 in the top duct of housing 11,the templates grooves 58 being located over exposed edges 68 of theinsulator sheets and cooperating therewith to center slots 59 over thetop edge 13 of busbars 12. Because the template 57 is ofa thicknesssufficient to fill substantially the air gap 19 above the busbars topedge 13, the slots 59 in and the ribs 66, 67 on the template cooperatewith the insulator sheet 15 to define stab chambers 70 insulated onefrom the other. The plugs stabs 60 are received vertically from outsidethe housing 11 to make electric contact with the edges 13 of the busbars12 in the stab chambers 70 so defined, see FIG. 3.

The template 57 is provided with a lip 74 extending from the forward 75and trailing 73 ends thereof, see FIGS. 2, 2B and 4-6. The axial lengthof the template 57 is such that, in cooperation with these lips 74, thetemplate 57 is mechanically supported on top edges 76 of the verticalreinforcing members and on the top face 27 of the side walls 16, therebysupporting same in the operating attitude within the take-off section51. Thus, the template 57 is not totally supported by the insulatorsheets 15 cooperating with the grooves 58 on the bottom face 65 thereof,although it may be so supported to some extent if desired. But the mainsupport of the template 57 in its operating environment comes from thelips 74 overlying certain support means which is a part of the bus ductshousing 11, namely, the top face 27 of the side walls 16 and the edges76 of the vertical reinforcing members 35. To assemble the template 57with the bus duct's housing 11, same is simply slipped into place overinsulator sheets 15. The tem plate 57 is held within the housing 11,once the top 17 of the housing is bolted in place to brackets 37, byvirtue of the rectangular hole 81 in the housings top being of smallerdimensions than the rectangular periphery of the template. This housingtop 1'7template 57 geometry provides a rectangular frame, so to speak,in the housings top that overlies the lips 74 and other peripheralportions of the template 57 to restrain same in its operatingenvironment, see FIGS. 2 and 218. It will be particularly noted thatthis allows a very simple method of assembly requiring no special toolsor skill on the part of the assembler.

The opening 81 in the housings top 17 is provided with a door 82 that ispivotable between a closed position (see bottom take-off section 51shown in FIG. 2) where access to the stab chambers 70 defined by thetemplate 57 and insulator sheets 15 is sealed from the environment ofthe bus duct 10, and an open position (see FIG. 1 and top take-offsection shown in FIG. 2) at which the stab chambers are exposed toreceive a plugs stabs 60. The door 82 is in the form ofa flat sheetmetal piece simply cut out of the housings top I7, and is provided withsubstantially the same external dimensions and configuration as theopening 81 in the top. The door 82 is pivotally mounted to the housingstop 17 by a hinge 83.

It is to be noted that the door 82 is flush with the top l7just asthough it were a part thereof when the door is closed. This is madepossible by the doors latch 72 which is, essentially, located on theunderside of the door, see FIGS. 2, 2A and 7. The top face 64 of thetemplate 57 is provided with a recessed forward section 71 to cooperatewith the latch 72, see FIG. 4. The latch 72 is in the form of a T-shapedpiece that includes a latch finger 84 at the forward end of a slideplate 85, the slide plate being mounted for reciprocable movementthrough a slot 78 therein that cooperates with a stud 86 fixed to thedoor 82. A leaf spring 87 is fixed to the slide plate opposite the latchfinger 84, the spring tending toward a straight line configuration atall times and having a tit 88 at each end received in notch 89 in theunderside of the door 82. The slide plate 85 and, hence; the latchfinger 84, are constantly urged toward the latching position where thelatch finger is extended out beyond the free edge 91 of the door 82, seeFIG. 2A. Of course, when the door 82 is in the closed attitude the latchfinger 84 extends beneath the housings top 17 so as to maintain the doorin the closed position. When the door 82 is in the open position whereitoverlies, and is positioned flush against, the housings top 17, thelatch finger 84 cooperates with a tab 92 raised out of the plane of (butwhich is fixed to) the housings top so as to maintain the door in theopen position and so that same does not swing closed or to someintermediate position; this is particularly useful when the bus duct ishung from a ceiling and when the plug 61 is installed on the undersidethereof.

The door 82 itself is opened, or is removed from engagement with theraised tab 92, by a hand tool inserted in slot 94 within latchs slideplate 85. When the door 82 is in the closed attitude, the slide plate issimply retracted until the latch finger 84 is removed from underneaththe housings top 17 (the slot 94 in the slide plate 85 is accessiblethrough a hole 95 formed in the door); the door is then lifted out ofthe same plane as the housings top 17. This manual operation is easilycarried out by an operator through use of a screwdriver. When closingthe door 82 from the open attitude where the latch finger 84 isrestrained beneath the raised tab 92, the screwdriver is inserted in theslot 94 and the slide plate retracted until the latch finger is removedfrom underneath the raised tab; the door is then simply pivoted closedon hinge 83.

As noted previously, it is preferred that the take-ofi sections 51 bepaired, one on the top 17 and one on the bottom 18 of the plug-in busduct 10, at each location along the axial 45 length of the bus duct.This allows freedom in installation of the bus duct 10 without worry asto which side 17 or 18 is most conveniently faced for futureinstallations of plug units 61 when same proves desirable. Further, andas mentioned, the plug-in bus duct of this invention makes use of thenovel structural concepts taught in U.S. Pat. application Ser. No.70,010, filed Sept. 8, 1970, invented by Paul M. Hafer and assigned tothe assignee of this application. Basically, the plug-in bus duct ofthis invention makes use of the bus duct structure taught in U.S. Pat.application Ser. No. 70,010, but includes at least one structurallyunique take-off section 51 in the bus ducts top or bottom between theends thereof. To the extent necessary, the description of U.S. Pat.application Ser. No. 70,010 is incorporated herein by reference tofacilitate understanding of the plug-in bus duct structure of thisinvention.

The ends (not shown) of the bus ducts housing 11 in the plug-in bus duct10 of this invention, and the ends (not shown) of the busbars 12themselves of the plug-in bus duct of this invention, may be formed asdescribed in connection with that bus duct taught in U.S. Pat.application Ser. No. 70,0l0. Further, the plug-in bus duct 10 of thisinvention may be employed with a busbar coupler system of the typetaught in US. Pat. No. 3,559,148, issued Jan. 26, 1971, invented by PaulM. Hafer and assigned to the assignee of this application. Further, aplug unit 61 of the type taught in US. Pat. application Ser. No.176,066, filed simultaneously herewith, invented by Paul M. Hafer, andassigned to the assignee of this application, may be employed with theplug-in bus duct of this invention.

Having described in detail the preferred embodiment of my invention,what I desire to claim and protect by Letters Patent is:

1. A plug-in bus duct comprising a group of elongated, flat busbarspositioned in sideby-side relation,

an elongated housing having side walls of a height substantially greaterthan the width of said busbars, thereby establishing an air gap betweenthe top edges of said busbars and the top of said housing and an air gapbetween the bottom edges of said busbars and the bottom of said housing,

structure defining a stab access opening in at least;

one of the top and bottom of said housing, said stab access openingcommunicating with one of said air gaps,

insulation means including insulator sheets of a width substantiallygreater than the width of said busbars disposed between said busbars andthe sides of said housing to separate said busbars one from the otherand from the sides of said housing, said busbars being separated onefrom the other and fromsaid side walls only by said insulation means,said insulation means being arranged to leave at least one of the topand bottom edges of said busbars exposed within the area of saidhousings stab access opening, and

a take-off section that allows power to be taken off said bus ductthrough a plug unit, said take-off section including an insulatortemplate that is in- 45 stalled within one of said air gaps adjacentsaid stab access opening, said template having a number of slots thatextend through said template from its top face to its bottom face andthat are equal to the number of said busbars, said template also havinga series of grooves on its bottom face aligned axially of said bus ductwith the width of each groove being approximately equal to the thicknessof its associated insulator sheet, said insulator sheets being receivedin said grooves and cooperating with said slots to define a series ofstab chambers insulated one from the other within said housing such thateach chamber can receive one stab from the plug unit through said stabaccess opening in electrical contact with the exposed edge ofa busbar.

2. A plug-in bus duct as set forth in claim 1 further 6 ble between aposition at which said stab access 5 opening is open so that said stabchambers can receive the plug unit's stabs and a position at which saidstab access opening is closed to the environment of said bus duct.

3. A plug-in bus duct as set forth in claim 1 wherein said template isprovided with a lip extending therefrom at each of its ends, said lipbeing adapted to rest on structure immobily fixed to said housing,thereby locating said template in spatial relation within that air gapwhere it is positioned.

4. A plug-in bus duct as set forth in claim 1 wherein said insulatortemplate is of a thickness substantially equal to the height of that airgap where it is positioned, and wherein said slots are staggered axiallyof said bus duct so that the slots serving two adjacent busbars are notin the same transverse plane.

5. A plug-in bus duct as set forth in claim 1 including a take-offsection on the top of said housing and a takeoff section on the bottomof said housing, said take-off sections being aligned substantiallytransversely to the axis of said bus duct.

6. A plug-in bus duct as set forth in claim 1 including a clip spanningsaid side walls adjacent each end of said take-off section along the topof said side walls, the spanning portion of each of said clips beingsubstantially spaced above said busbars,

a clip spanning'said side walls adjacenteachend of said take-off sectionalong the bottom of said side walls, the spanning portion of each ofsaid clips being substantially spaced below said busbars,

all of said clips serving to restrain mechanically said busbar group andsaid side walls compact sideby-side relation.

7. A plug-in bus duct as set forth in claim 6 wherein said top andbottom clips are positioned in pairs, each pair comprising a top clipand a bottom clip and being in a plane substantially transverse to theaxis of said bus duct, and wherein said clips are substantially U-shapedand fitted over the top edges and bottom edges of said side walls, thelegs of said clips being positioned on the outside of said side walls.

8. A plug-in bus duct as set forth in claim 7 wherein said housingfurther includes an H-shaped reinforcing member positioned against eachof said side walls in the area of said take-off sections for reinforcingsaid housing configuration, the legs of said l-Lshaped members beingpositioned substantially transverse to the axis of said bus duct, andsaid l-l-shaped members being restrained in position against said sidewall by said top clips and said bottom clips.

9. A plug-in bus duct comprising a group of elongated, flat busbarspositioned in side by-side relation,

an elongated housing having side walls of a height substantially greaterthan the width of said busbars, thereby establishing a gap between thetop edges of said busbars and the top of said housing and a gap betweenthe bottom edges of said busbars and the bottom of said housing,

structure defining a stab access opening in at least one of the top andbottom of said housing, said stab access opening communicating with oneof said gaps,

insulation disposed between said busbars and the sides of said housingto separate said busbars one from the other and from the sides of saidhousing,

one of the top and bottom edges of each of said busbars being exposedwithin said housing in the area of said stab access opening, and saidbusbars and said insulation and said side walls being positioned insandwich configuration with no air gaps therebetween, and

a take-off section that allows power to be taken off said bus ductthrough a plug unit, all of said busbars being planar in configurationfrom one end of said bus duct to the other including those portionswithin said take-off section, and said takeoff section including aninsulator template located within said stab access opening, saidtemplate defining a series of stab chambers adapted to cooperate withthe exposed edges of said busbars and insulated one from the otherwithin said housing such that each chamber may receive one stab from theplug unit through said stab access opening into electrical contact withthe exposed edge of a busbar. I

10. A plug-in bus duct as set forth in claim 9 further includingstructure defining at least one stab access opening in both the top andbottom of said housing, and an insulator template located within each ofsaid stab access openings, thereby allowing the plug units stabs toelectrically contact either of the top and bottom edges of said busbars.

11. A plug-in bus duct as set forth in claim 9 wherein the stab chambersdefined in said insulator template are staggered axially of said busduct so that no two adjacent stab chambers are in the same planetransverse to said bus duct.

12. A plug-in bus duct as set forth in claim 9 i'ncluding a take-offsection on the top of said housing and a take-off section on the bottomof said housing, said take-off sections being aligned substantiallytransversely to the axis of said bus duct.

13. A plug-in bus duct as set forth in claim 12 including a clipspanning said side walls adjacent each end of said take-off sectionalong the top of said side walls, the spanning portion of each of saidclips being substantially spaced above said busbars, and

a clip spanning said side walls adjacent each end of said take-offsection along the bottom of said side walls, the spanning portion ofeach of said clips being substantially spaced below said busbars,

all of said clips serving to restrain mechanically said busbar group andsaid side walls in compact sideby-side relation.

14. A plug-in bus duct as set forth in claim 13 wherein said top andbottom clips are positioned in pairs, each pair comprising a top clipand a bottom clip and being in a plane substantially transverse to theaxis of said bus duct, and wherein said clips are substantially U-shapedand fitted over the top edges and bottom edges of said side walls, thelegs of said clips being positioned on the outside of said side walls.

15. A plug-in bus duct as set forth in claim 14 wherein said housingfurther includes an H-shaped reinforcing member positioned against eachof said side walls in the area of said take-off sections for reinforcingsaid housing configuration,

the lags of said H-shaped members being positlone substantiallytransverse to the axis 0 said bus duct, and said H-shaped members beingrestrained in position against said side walls by said top clips andsaid bottom clips.

1. A plug-in bus duct comprising a group of elongated, flat busbars positioned in side-by-side relation, an elongated housing having side walls of a height substantially greater than the width of said busbars, thereby establishing an air gap between the top edges of said busbars and the top of said housing and an air gap between the bottom edges of said busbars and the bottom of said housing, structure defining a stab access opening in at least one of the top and bottom of said housing, said stab access opening communicating with one of said air gaps, insulation means including insulator sheets of a width substantially greater than the width of said busbars disposed between said busbars and the sides of said housing to separate said busbars one from the other and from the sides of said housing, said busbars being separated one from the other and from said side walls only by said insulation means, said insulation means being arranged to leave at least one of the top and bottom edges of said busbars exposed within the area of said housing''s stab access opening, and a take-off section that allows power to Be taken off said bus duct through a plug unit, said take-off section including an insulator template that is installed within one of said air gaps adjacent said stab access opening, said template having a number of slots that extend through said template from its top face to its bottom face and that are equal to the number of said busbars, said template also having a series of grooves on its bottom face aligned axially of said bus duct with the width of each groove being approximately equal to the thickness of its associated insulator sheet, said insulator sheets being received in said grooves and cooperating with said slots to define a series of stab chambers insulated one from the other within said housing such that each chamber can receive one stab from the plug unit through said stab access opening in electrical contact with the exposed edge of a busbar.
 2. A plug-in bus duct as set forth in claim 1 further comprising a cover fixed to said housing, said cover being pivotable between a position at which said stab access opening is open so that said stab chambers can receive the plug unit''s stabs and a position at which said stab access opening is closed to the environment of said bus duct.
 3. A plug-in bus duct as set forth in claim 1 wherein said template is provided with a lip extending therefrom at each of its ends, said lip being adapted to rest on structure immobily fixed to said housing, thereby locating said template in spatial relation within that air gap where it is positioned.
 4. A plug-in bus duct as set forth in claim 1 wherein said insulator template is of a thickness substantially equal to the height of that air gap where it is positioned, and wherein said slots are staggered axially of said bus duct so that the slots serving two adjacent busbars are not in the same transverse plane.
 5. A plug-in bus duct as set forth in claim 1 including a take-off section on the top of said housing and a take-off section on the bottom of said housing, said take-off sections being aligned substantially transversely to the axis of said bus duct.
 6. A plug-in bus duct as set forth in claim 1 including a clip spanning said side walls adjacent each end of said take-off section along the top of said side walls, the spanning portion of each of said clips being substantially spaced above said busbars, a clip spanning said side walls adjacent each end of said take-off section along the bottom of said side walls, the spanning portion of each of said clips being substantially spaced below said busbars, all of said clips serving to restrain mechanically said busbar group and said side walls in compact side-by-side relation.
 7. A plug-in bus duct as set forth in claim 6 wherein said top and bottom clips are positioned in pairs, each pair comprising a top clip and a bottom clip and being in a plane substantially transverse to the axis of said bus duct, and wherein said clips are substantially U-shaped and fitted over the top edges and bottom edges of said side walls, the legs of said clips being positioned on the outside of said side walls.
 8. A plug-in bus duct as set forth in claim 7 wherein said housing further includes an H-shaped reinforcing member positioned against each of said side walls in the area of said take-off sections for reinforcing said housing configuration, the legs of said H-shaped members being positioned substantially transverse to the axis of said bus duct, and said H-shaped members being restrained in position against said side wall by said top clips and said bottom clips.
 9. A plug-in bus duct comprising a group of elongated, flat busbars positioned in side-by-side relation, an elongated housing having side walls of a height substantially greater than the width of said busbars, thereby establishing a gap between the top edges of said busbars and the top of said housing and a gap between the bottom edges of said busbars and the bottom of said housing, structure defining a stab accesS opening in at least one of the top and bottom of said housing, said stab access opening communicating with one of said gaps, insulation disposed between said busbars and the sides of said housing to separate said busbars one from the other and from the sides of said housing, one of the top and bottom edges of each of said busbars being exposed within said housing in the area of said stab access opening, and said busbars and said insulation and said side walls being positioned in ''sandwich'' configuration with no air gaps therebetween, and a take-off section that allows power to be taken off said bus duct through a plug unit, all of said busbars being planar in configuration from one end of said bus duct to the other including those portions within said take-off section, and said take-off section including an insulator template located within said stab access opening, said template defining a series of stab chambers adapted to cooperate with the exposed edges of said busbars and insulated one from the other within said housing such that each chamber may receive one stab from the plug unit through said stab access opening into electrical contact with the exposed edge of a busbar.
 10. A plug-in bus duct as set forth in claim 9 further including structure defining at least one stab access opening in both the top and bottom of said housing, and an insulator template located within each of said stab access openings, thereby allowing the plug unit''s stabs to electrically contact either of the top and bottom edges of said busbars.
 11. A plug-in bus duct as set forth in claim 9 wherein the stab chambers defined in said insulator template are staggered axially of said bus duct so that no two adjacent stab chambers are in the same plane transverse to said bus duct.
 12. A plug-in bus duct as set forth in claim 9 including a take-off section on the top of said housing and a take-off section on the bottom of said housing, said take-off sections being aligned substantially transversely to the axis of said bus duct.
 13. A plug-in bus duct as set forth in claim 12 including a clip spanning said side walls adjacent each end of said take-off section along the top of said side walls, the spanning portion of each of said clips being substantially spaced above said busbars, and a clip spanning said side walls adjacent each end of said take-off section along the bottom of said side walls, the spanning portion of each of said clips being substantially spaced below said busbars, all of said clips serving to restrain mechanically said busbar group and said side walls in compact side-by-side relation.
 14. A plug-in bus duct as set forth in claim 13 wherein said top and bottom clips are positioned in pairs, each pair comprising a top clip and a bottom clip and being in a plane substantially transverse to the axis of said bus duct, and wherein said clips are substantially U-shaped and fitted over the top edges and bottom edges of said side walls, the legs of said clips being positioned on the outside of said side walls.
 15. A plug-in bus duct as set forth in claim 14 wherein said housing further includes an H-shaped reinforcing member positioned against each of said side walls in the area of said take-off sections for reinforcing said housing configuration, the legs of said H-shaped members being positioned substantially transverse to the axis of said bus duct, and said H-shaped members being restrained in position against said side walls by said top clips and said bottom clips. 